1. Field of the Invention
The present invention relates to an add-on card for wireless communication with a personal digital assistant (PDA), and more particularly, to an add-on card for wireless communication with a power-managing circuit for managing the power supplied.
2. Description of the Prior Art
Modern electrical technological advancements have vastly decreased the size of a personal computer. Some portable computers are light enough and small enough to be put in a pocket. They are called pocket or palm-sized computers, such as the personal digital assistant (PDA).
The expansion, or add-on card, is a card which contains electronic devices and is inserted in a socket formed in such a portable personal computer in order to improve its performance or functionality. Recently, the relative socket and the expansion cards have been widely standardized. The socket of the PDA has to provide the current needed by the circuitry of the add-on card for the card to work properly.
With the increasing popularity of PDAs, there has been a similar increase into researching various functioned add-on cards to improve the PDAs performance. If every add-on card is suitable for the standard socket, the PDA can be relatively low cost and convenient to expand functionality. However, because the power supplied from the standard socket of the CF card is limited, it limits the add-on cards functionality. The highest current supplied from the standard socket of the PDA is about 550 milliampere (1 milliampere= 1/1000 ampere). If the add-on card needs more current to operate normally than the specification of the standard socket of the PDA provides, the PDA cannot utilize this add-on card to improve its functionality. For example, a desired transient current of an RF circuit for transmitting or receiving the RF signal operating in wireless communication is about 2000 milliampere. Therefore, the RF circuit cannot be located in the add-on card due to the insufficient current of the socket, and the PDA cannot be improved in the field of the wireless communication by using the standard socket of the CF card.